Conventionally, a locking device for cars, for example, comprises a plurality of cylinder locks corresponding to locking portions in the car and a key plate capable of unlocking these cylinder locks. The cylinder lock has a case and a rotor rotatable within the case. The rotor has a disk tumbler or pin tumbler therein to form a lock-side unlocking code.
The key plate for unlocking these cylinder locks has a key-side unlocking code set in a code forming portion. With the key plate inserted in the rotor, the tumbler occupies a predetermined position in the rotor, which is uniquely determined by the code forming portion. The tumbler position in the rotor and the rotate enable/disable state of the rotor are related with each other by an appropriate mechanism, so that only when a key plate having an unlocking code that matches the lock-side unlocking code is inserted, the rotor can be turned.
The conventional locking device, however, has the following drawback. That is, the lock-side unlocking code of the cylinder lock is determined beforehand during the assembly of the cylinder lock according to the kind and arrangement of the tumbler. Therefore, when a plurality of cylinder locks provided in, for example, doors, trunk and steering are to be locked or unlocked by the same key plate for each vehicle, the plurality of cylinder locks incorporating the tumblers having the same unlocking codes need to be managed as one group together with the key plate. If a cylinder lock which is outside the group management is assembled into the car, the locking portion provided by that cylinder lock cannot be accessed.
On the other hand, although cars are assembled in an automated production line, the cylinder locks described above each have a characteristic unlocking code. Therefore, the cylinder locks cannot be interchanged in the event of a failure or when some parts are not available. Further, because these cylinder locks must be handled as one group, the efficiency of car assembly deteriorates.
In a car production line or during a process of building houses, it is effective in improving the work efficiency to allow unspecified workers to unlock the door to enter a car or house. However, if, after installing a cylinder lock in a car or house, the worker inadvertently locks the door, only a person who owns a genuine key can enter the car or house, thereby significantly degrading the efficiency.
The present invention has been accomplished to overcome the above drawback and its object is to provide a cylinder lock which allows the unlocking code to be set easily at any desired time after the cylinder lock has been assembled, thereby improving the workability of car assembly.